The present invention is directed to terminating the ends of lengths of corrugated metal foil wrap tubing, and more particularly to a method and apparatus for end-forming such tubing.
Metal foil wrap corrugated tubing, also referred to as convoluted multi-ply shielding, has been employed as a protective sheathing in automotive and other applications. For example, metal foil wrap tubing is employed to protect delicate or thermally sensitive items, such as electrical wires, fuel lines and plastic tubes with low heat resistance, from exterior abrasion or heat. Metal foil wrap corrugated tubing is also employed to sheathe high temperature tubes, such as tubes conducting exhaust gas, from adjacent exterior thermally sensitive items such as electrical wires and fuel lines. Such metal foil wrap corrugated tubing may be readily bent and formed around objects and turns, and provides good protection against abrasion of the internal electrical wires. One line of metal foil wrap corrugated tubing is marketed by Clevaflex, Ltd. of Cleveland, Ohio. In general, such tubing comprises an elongated strip of layered material, including metal such as stainless steel, spirally wound into a tube, mechanically locked in place by microcorrugations and bonded with a thermosetting adhesive. When the tubing is cut to desired length, steps must be taken to prevent unwrapping at the end of the spirally wrapped corrugated metal, particularly at high temperatures at which the adhesive may lose adhesion. This is conventionally accomplished by crimping or otherwise securing an end cap or ferrule to the end of the tube. These end caps are expensive relative to the cost of the tubing itself.
It is therefore a general object of the present invention to provide a method and apparatus for forming the end of a length of metal foil wrap corrugated tubing that prevent unwrapping at the tubing end, that do not damage the tubing length, and that are adapted for automated implementation. Another object of the invention is to provide a length of metal foil wrap corrugated tubing having a formed end to prevent unwrapping of the tubing material, but without use of additional components such as the conventional end caps.
A method of forming an end of corrugated metal foil wrap tubing in accordance with one aspect of the present invention includes providing a length of tubing having a sidewall with spaced corrugations and folding a portion of the end of the tubing into the sidewall to form a sidewall end portion of inner and outer layers. The sidewall end portion is preferably additionally axially compacted by axially compressing the end portion to bring the corrugations into axial abutment. The end portion of the tubing preferably is folded inwardly into itself by bringing the end portion into axial engagement with a folding tool. In the preferred embodiment of the invention, this axial engagement is continued to compact the end portion of the tube in an annular end channel on the compacting tool. By folding the tubing end inwardly upon itself and then axially compacting the corrugations as in the preferred embodiment of the invention, a tight end joint is formed to resist unwrapping or unraveling of the metal foil.
In the preferred embodiment of the invention, a length of metal foil wrap corrugated tubing is clamped between jaws for holding the tubing during contact with the compacting tool. These jaws preferably are provided as an opposed set of jaws that have rib segments which, when the jaws are closed around the tubing, form a circumferentially continuous rib to indent a channel around the periphery of the tubing adjacent to the end portion of the tubing. This channel serves both to enhance clamping of the tubing between the jaws against axial forces applied to the tubing by the compacting tool, and to isolate the end portion of the tubing from the remainder of the tubing length during the end-forming operation. In the preferred embodiment of the invention, the compressing operation is preceded by a folding operation, in which the end of the tubing is brought into engagement with a fold-over tool that folds the end of the tubing radially inwardly. This folded portion of the tubing is then engaged by a horn that extends axially from the compacting tool further to fold the end axially into the tubing end portion prior to engagement of the tubing with the channel in the compacting tool. The same set of clamping jaws may be employed to clamp the tubing during both the folding and the compacting operations. In the preferred embodiment of the invention, the folding operation is preceded by a crimping operation, in which the end of the tubing is crimped radially inwardly by a plurality of crimping jaws acting against a conical surface on a mandrel within the tubing.
Thus, in its most preferred form, the present invention provides a method for forming a free end of a length of metal foil wrap corrugated tubing in which the free end of the tubing is first crimped against a mandrel, then folded to extend radially inwardly, then folded further to extend axially inwardly within the inside diameter of the tubing end, and then compacted axially to bring the corrugations into facing abutment with each other and tighten the formed end of the tubing against unraveling of the metal foil. The crimping operation involves closure of a plurality of jaws around the free end of the tubing and deforming the tubing end against a tapering surface on an internal mandrel. The tubing is then gripped between jaws that form a radially indented channel in the periphery of the tubing, both to enhance the clamping action of the jaws and to isolate the formed end of the tubing from the remainder of the tubing. The clamped length of tubing is then engaged by a fold-over tool to fold the crimped end of the tubing radially inwardly, and then by a compacting tool further to fold the end axially into the tubing and then to compact the end portion of the tubing to form a tight tubing end joint.
Apparatus for forming an end-of corrugated metal foil wrap tubing in accordance with the preferred embodiment of another aspect of the invention includes a set of jaws for closing around a length of foil wrap tubing to clamp the tubing, and for opening to release the tubing. A compacting tool has an axially extending horn and an annular axially facing end channel. The compacting tool is brought into engagement with an end portion of a length of tubing in the jaws so as to fold the end portion into itself and compact the end portion by axially compressing the end portion to bring corrugations in the end portion into axial abutment with each other. In the preferred embodiment of the invention, the apparatus also includes a folding tool having an annular axially facing end channel. The folding tool is brought into axial engagement with the end of the tubing, prior to the compacting tool, so as to fold a portion of the end radially inwardly. Subsequent engagement by the compacting tool deforms this portion of the tubing end axially inwardly by contact with the horn on the compacting tool, and then axially compacts the end portion by engagement with the end channel in the compacting tool. The jaws preferably have arcuate rib segments that, when the jaws are clamped around a length of tubing, form a circumferentially continuous rib that indents a circumferential channel in the tubing to grip the tubing and to isolate the end portion from the remainder of the tubing.
A length of corrugated metal foil wrap tubing in accordance with a third aspect of the present invention has a formed end that includes an external end portion in which tubing corrugations are axially compacted together, and an internal end portion integrally folded inward from an axial end of the external end portion and in radially internal abutment with the external end portion. The formed end preferably also has a circumferential channel in the tubing separating the form end from the remainder of the tubing length.